This study is a physical chemical study into the nature of the structure of the ribosomal subunits from the bacteria E. coli. The ribosomal proteins are isolated and characterized as to isolated physical properties. Solutions of mixtures of the proteins are subsequently analyzed principally by analytical ultracentrifugation techniques for molecular interactions. The thermodynamics of interaction are to be obtained in order to provide an interpretation of principal sites of interaction within the structure and types of interacting sites between the components. The study should reveal the network of interactions that may occur within the systems. If the isolated interactions in solution persist in the total structure than a two dimensional energy versus pair member diagram can be utilized to construct a three dimensional diagram of the ribosomal structure. The studies have found and are continuing to study interactions between proteins S3-S5, S5-S10, S3-S4 and S4-S5 in addition to having observed no interaction between several other pairs of proteins in the small subunit of the E. coli ribosome. It is expected that the study will also examine the role of other factors in the protein synthesis mechanism for influence on the observed interactions as well as an examination of the interactions that occur between subunits. BIBLIOGRAPHIC REFERENCES: M.F. Rohde, S. O'Brien, S. Cooper, and K.C.Aune, Physical Properties of Some Ribosomal Proteins in Solution and Evidence for Molecular Interactions between Isolated Ribosomal Proteins, Biochemistry, 14, 1079-1087, (1975) J. Stoops, M. Arslanian, Y.H. Oh, K. C. Aune, T.C. Vanaman, and S. J. Wakil, The Presence of Two Polypeptide Chains Comprising the Fatty Acid Synthetase, Proc. Nat. Sci. (USA), 72, 1940-1944, (1975).